(a) Field of the Invention
The present invention relates to a method of preparing iodinated aromatic compounds, and more specifically to a method of preparing iodinated aromatic compounds comprising: subjecting a mixture including an aromatic compound, a di-iodo aromatic compound or water, and iodine (I2) to iodination in the presence of a zeolite catalyst and oxygen.
(b) Description of the Related Art
The preparation method of the halogenated aromatic compounds using reactants including an aromatic compound such as benzene or naphthalene, and a halogen (bromine, chlorine, iodine, etc.) has been focused on throughout the industrial field. Specifically, among the above halogenated aromatic compounds, p-di-iodo benzene (p-DIB) is widely used as the reactant for the manufacture of polyphenylene sulfide (PPS), and it is commercially valuable, and accordingly studies on improving the productivity of p-DIB have been actively carried out.
For example, as shown in FIG. 1, U.S. Pat. No. 4,778,938 and U.S. Pat. No. 4,746,758 disclose a preparation method of p-DIB using benzene and iodine (I2) as reactants in the presence of a zeolite catalyst and oxygen. According to those prior arts, these preparation methods have advantages in conversion rate in p-DIB productivity. Further, according to the disclosure of the above prior arts, these methods can also minimize the oxidation reaction of the benzene or naphthalene.
However, the above method has a disadvantage in controlling the iodinating reactor temperature, which is related to a locally occurring massive exothermic reaction. As a general rule, the oxidation of the hydrogen iodide (hydroiodic acid, HI) is necessarily accompanied with iodination of aromatic compounds in the presence of a zeolite catalyst and oxygen. This oxidation of HI is a massive exothermic reaction, and thus elevates the temperature of the center of the iodinating reactor. Under this elevated temperature condition, not only the iodination, but also the combustion reaction of reactants is vigorous, and thus brings about a massive runaway reaction. Furthermore, when applying these preparation methods to the plant scale and designing said plant, temperature control becomes more important and is preferentially considered, because the diameter of the reactor should be designed to be sufficiently large.
In addition, under this elevated temperature condition, combustion reaction of the reactants, in accordance with formation of impurities such as carbon deposits, make the catalyst inactive and thus shorten the replacement period of the catalyst. Further, due to the difficulty in controlling the temperature of the iodinating reactor, the feeding flux of the reactants cannot be increased, and a drop in productivity occurs.